The invention relates to an apparatus on a spinning preparation machine, for example, a flat card, draw frame or the like, for monitoring at least one sliver, having two rotating rollers that form a roller nip through which at least one sliver passes.
Feeding of the sliver to the revolving plate of a can coiler is effected at the output of a flat card via take-off rollers. In a known apparatus, (DE 40 28 365 A), an optical sensor, which detects whether a fibre sliver is located in its field of vision or not, is arranged downstream of the take-off rollers. The sensor monitors the presence or absence of the sliver. Absence of the sliver is reported as a malfunction to a machine control. The sensor is arranged away from the roller nip at a distance from the take-off rollers. The optical path of the sensor runs perpendicular to the roller axles. The tension of the sliver changes at a distance from the take-off rollers, that is, the sliver sags to different depths. At relatively high and high sliver speeds, the sliver additionally oscillates parallel to the axles of the take-off rollers, that is, the sliver disappears from the optical path of the sensor, although no sliver funnel is present. Reliable monitoring of sliver breakage is not possible with the known apparatus. In addition, it is inconvenient that the spacing necessitates a separate holding device for the sensor.
It is an aim of the invention to produce an apparatus of the kind described initially that avoids or mitigates the said disadvantages, is in particular of simple construction and permits a reliable and trouble-free monitoring of sliver breakage.